Frost heaving Facts for Kids

Frost heaving happens when water in the soil freezes and expands. This can push the ground upwards. If the frozen water never thaws, it's called permafrost. This natural process can cause big problems for roads, buildings, and even plants.

What is Frost Heaving?
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What is Frost Heaving?

Frost heaving is a natural process where the ground swells or lifts because of ice forming in the soil. It happens when the temperature of the soil drops below freezing point, and there's enough water present. This can create large ice formations that push the soil and anything on top of it upwards.

How Does Ice Push the Ground?

When water freezes, it expands by about 9%. But frost heaving isn't just about this small expansion. The real lifting power comes from something called ice lenses.

Ice lenses are layers of ice that grow larger and larger within the soil.
They form when water from deeper, unfrozen parts of the soil is drawn upwards towards the freezing front.
As this water reaches the cold area, it freezes onto existing ice crystals, making the ice lenses thicker.
This continuous growth of ice lenses pushes the soil above them upwards, causing the ground to heave.

The Role of Water and Soil

For frost heaving to happen, three main things are needed:

Freezing temperatures: The soil temperature must be below 0°C (32°F).
Water: There must be a source of water in the soil. This can be from rain, melting snow, or groundwater.
Specific soil types: Soils like silt and clay are most likely to experience frost heaving. This is because their tiny particles allow water to move through them easily, but also hold onto water well. Sandy or gravelly soils, which drain quickly, are less likely to heave.

Where Does Frost Heaving Occur?

Frost heaving is common in places with cold winters where the ground freezes and thaws.

Cold climates: Areas that experience long periods of freezing temperatures are prone to frost heaving.
Seasonal freezing: Even in places where the ground only freezes for part of the year, frost heaving can occur.
Permafrost regions: In areas with permafrost (ground that stays frozen for at least two years), frost heaving can create unique landforms.

Effects on Our World

Frost heaving can cause significant damage to human-made structures and natural environments:

Roads and sidewalks: It can crack and buckle roads, making them uneven and dangerous.
Buildings: Foundations of buildings can shift, leading to cracks in walls or structural damage.
Pipelines: Underground pipes can break or become misaligned.
Plants and crops: Plants can be pushed out of the ground, damaging their roots and making them unable to survive. This is sometimes called "frost pull" or "frost lift."
Natural landscapes: It can create interesting patterns on the ground, like stone circles or mounds.

How Do We Deal with Frost Heaving?

Engineers and builders use different methods to prevent or reduce the damage caused by frost heaving:

Drainage: Improving drainage around structures helps remove water from the soil, reducing the amount available to freeze.
Insulation: Adding insulation layers under roads or foundations can help keep the soil from freezing.
Non-frost-susceptible materials: Using gravel or crushed rock as a base layer can prevent ice lenses from forming.
Deeper foundations: Building foundations below the deepest frost line (the depth to which the ground freezes) can protect them from heaving.

Images for kids

Ice lens formation resulting in frost heave in cold climates.
Frost heaves on a rural Vermont road during spring thaw
Partially melted and collapsed lithalsas (heaved mounds found in permafrost) have left ring-like structures on the Svalbard Archipelago
Palsas (heaving of organics-rich soils in discontinuous permafrost) may be found in alpine areas below Mugi Hill on Mount Kenya.